How to let a CFrameWnd based SDI application start in full screen?

I have a CFrameWnd based SDI application. I want it to start in full
screen. I did the following:

BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
{
  ...
  cs.style = WS_OVERLAPPED | WS_CAPTION | WS_MAXIMIZE
  cs.dwExStyle &= ~WS_EX_CLIENTEDGE;
  cs.lpszClass = AfxRegisterWndClass(0);
  return TRUE;
}

This will start full screen on my development machine. But after
deploying it, it doesn't start in full screen on other machines.

Then I overrided the following method:

void CMainFrame::OnSetFocus(CWnd* /*pOldWnd*/)
{
  // forward focus to the view window
  m_wndView.SetFocus();

  if (!m_bFullScreen)
  {
    m_bFullScreen = true;

    int cyCaption = ::GetSystemMetrics(SM_CYCAPTION);
    int cxFrame = ::GetSystemMetrics(SM_CXFRAME);
    int cyFrame = ::GetSystemMetrics(SM_CYFRAME);
    int cxScreen = ::GetSystemMetrics(SM_CXSCREEN);
    int cyScreen = ::GetSystemMetrics(SM_CYSCREEN);

    SetWindowPos(NULL, -cxFrame, -(cyFrame + cyCaption), cxScreen + 2
* cxFrame, cyScreen + 2 * cyFrame + cyCaption, SWP_NOZORDER);
  }
}

This will occupy most of the screen, but not the taskbar at the
bottom. How can I also let the application occupy really the full
screen (includeing the taskbar area)? Thanks.

Leo